Direct current (DC) motors use an electrical current flowing in one direction, (as opposed to an alternating current) to quickly switch the polarity of an electromagnet back an forth. This electromagnet is fixed within a cylindrical magnet, and when electrical current is applied, the switching polarity of the electromagnet causes it to spin. Stall torque is the amount of torque it takes to stop a motor from moving. Torque is measured in Newton-Meters. A stall torque of one Newton-Meter means that it takes one newton of force perpendicularly to a one meter arm on the motor
shaft, to stop the motor from spinning. The purpose of our experiment is to see how the output of different sized motors changes depending on their operating voltage.
Procedure
We took ten DC motors of varying sizes, and attached each one to a propeller with a 6.5 cm radius. To measure each motor's stall torque, we held each motor perpendicular to a scale, and attached the motors to a 9 volt DC power supply. When the motor spun, the tip of the propeller pressed against the scale, and we recorded the amount of force shown in ounces. Then we repeated the procedure using a six volt battery instead of the nine volt power supply. Then we converted the force in ounces to Newtons, and multiplied the number of Newtons by 6.5 to calculate the motors stall torque in newton-centimeters. We then graphed our results.
Results
motor mass
stall torque in n-cm at 9 volts
stall torque in n-cm at 6 volts
203.2
2.93
4.81
70.8
0.54
0.98
66.0
0.72
1.50
55.6
0.78
0.91
50.6
1.11
1.30
49.9
0.62
0.98
27.9
0.51
0.51
19.5
0.38
0.42
16.8
0.38
0.25
16.5
0.29
0.36
Y= stall torque in newton-centimeters X= motor mass in grams
Conclusions
When smaller motors operate at a higher voltage, their power outputs do not increase significantly, and in some cases even decrease. On the other hand when larger motors receive more volts their power output rises greatly, in some cases doubling. Errors might have come from variance in the where the propeller touched the scale, although we were careful to keep it constant. Our results matched what we expected, save for the one motor that produced more power with 6 volts that with 9 volts. With that motor we repeated the test several times, and the results were consistent. To improve this experiment we would have tried to use a few more voltages, and include a greater variety of motors.
References
Newton Meter, updated March 8, 2008, accessed January 27, 2008
How Different Sized Motor's Outputs Change Depending on Operating Voltage
Ben, Kostya
Table of Contents
Introduction
Direct current (DC) motors use an electrical current flowing in one direction, (as opposed to an alternating current) to quickly switch the polarity of an electromagnet back an forth. This electromagnet is fixed within a cylindrical magnet, and when electrical current is applied, the switching polarity of the electromagnet causes it to spin. Stall torque is the amount of torque it takes to stop a motor from moving. Torque is measured in Newton-Meters. A stall torque of one Newton-Meter means that it takes one newton of force perpendicularly to a one meter arm on the motorshaft, to stop the motor from spinning. The purpose of our experiment is to see how the output of different sized motors changes depending on their operating voltage.
Procedure
We took ten DC motors of varying sizes, and attached each one to a propeller with a 6.5 cm radius. To measure each motor's stall torque, we held each motor perpendicular to a scale, and attached the motors to a 9 volt DC power supply. When the motor spun, the tip of the propeller pressed against the scale, and we recorded the amount of force shown in ounces. Then we repeated the procedure using a six volt battery instead of the nine volt power supply. Then we converted the force in ounces to Newtons, and multiplied the number of Newtons by 6.5 to calculate the motors stall torque in newton-centimeters. We then graphed our results.
Results
Y= stall torque in newton-centimeters X= motor mass in grams
Conclusions
When smaller motors operate at a higher voltage, their power outputs do not increase significantly, and in some cases even decrease. On the other hand when larger motors receive more volts their power output rises greatly, in some cases doubling. Errors might have come from variance in the where the propeller touched the scale, although we were careful to keep it constant. Our results matched what we expected, save for the one motor that produced more power with 6 volts that with 9 volts. With that motor we repeated the test several times, and the results were consistent. To improve this experiment we would have tried to use a few more voltages, and include a greater variety of motors.References
Newton Meter, updated March 8, 2008, accessed January 27, 2008